Package edu.wisc.ssec.mcidasv.util.pathwatcher

Class SimpleDirectoryWatchService

java.lang.Object

edu.wisc.ssec.mcidasv.util.pathwatcher.SimpleDirectoryWatchService

All Implemented Interfaces:

DirectoryWatchService, Service, Runnable

public class SimpleDirectoryWatchService
extends Object
implements DirectoryWatchService, Runnable

A simple class which can monitor files and notify interested parties (i.e. listeners) of file changes. This class is kept lean by only keeping methods that are actually being called.

Field Summary

Fields

Modifier and Type	Field	Description
private static final org.slf4j.Logger	logger	Logging object.
private final Map<Path,Set<OnFileChangeListener>>	mDirPathToListenersMap	Mapping of Paths to the Set of OnFileChangeListeners listening for changes to the associated Path.
private final AtomicBoolean	mIsRunning	Whether or not this DirectoryWatchService is running.
private final Map<OnFileChangeListener,Set<PathMatcher>>	mListenerToFilePatternsMap	Mapping of OnFileChangeListeners to the Set of patterns being used to observe changes in Paths of interest.
private final Map<WatchKey,Path>	mWatchKeyToDirPathMap	Mapping of monitoring "registration" keys to the Path that it will be watching.
private final WatchService	mWatchService	WatchService used to monitor changes in various Paths.

Constructor Summary

Constructors

Constructor	Description
SimpleDirectoryWatchService()	A simple no argument constructor for creating a SimpleDirectoryWatchService.

Method Summary

Modifier and Type	Method	Description
private static <T> WatchEvent<T>	cast(WatchEvent<?> event)	Utility method used to make "valid" casts of the given event to a specific type of WatchEvent.
private Path	getDir(OnFileChangeListener listener)	Get the Path associated with the given OnFileChangeListener.
private Path	getDirPath(WatchKey key)	Get the path associated with the given WatchKey.
private Set<OnFileChangeListener>	getListeners(Path path)	Get the OnFileChangeListeners associated with the given path.
private Set<PathMatcher>	getPatterns(OnFileChangeListener listener)	Get the Set of patterns associated with the given OnFileChangeListener.
private WatchKey	getWatchKey(Path dir)	Get the monitoring "registration" key associated with the given Path.
boolean	isRunning()	Checks to see if the service is still running.
private Set<OnFileChangeListener>	matchedListeners(Path dir, Path file)	Get the Set of OnFileChangeListeners that should be notified that file has changed.
private static PathMatcher	matcherForGlobExpression(String globPattern)	Returns a PathMatcher that performs "glob" matches with the given globPattern against the String representation of Path objects.
static boolean	matches(Path input, PathMatcher pattern)	Check the given input Path against the given pattern.
private static boolean	matchesAny(Path input, Set<PathMatcher> patterns)	Check the given input Path against all of the specified patterns.
private void	notifyListeners(WatchKey key)	Method responsible for notifying listeners when a file matching their relevant pattern has changed.
private void	notifyListenersOfInvalidation(WatchKey key)	Method responsible for notifying listeners when the path they are watching has been deleted (or otherwise "invalidated" somehow).
void	register(OnFileChangeListener listener, String dirPath, String... globPatterns)	Notifies the implementation of this interface that dirPath should be monitored for file system events.
void	run()
void	start()	Start this SimpleDirectoryWatchService instance by spawning a new thread.
void	stop()	Stop this SimpleDirectoryWatchService thread.
void	unregister(OnFileChangeListener listener)	Notifies the implementation of this interface that listener should cease to be notified of file system events.
void	unregisterAll()	Unregisters all listeners.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

logger

private static final org.slf4j.Logger logger

Logging object.

mWatchService

private final WatchService mWatchService

WatchService used to monitor changes in various Paths.

mIsRunning

private final AtomicBoolean mIsRunning

Whether or not this DirectoryWatchService is running.

mWatchKeyToDirPathMap

private final Map<WatchKey,Path> mWatchKeyToDirPathMap

Mapping of monitoring "registration" keys to the Path that it will be watching.

mDirPathToListenersMap

private final Map<Path,Set<OnFileChangeListener>> mDirPathToListenersMap

Mapping of Paths to the Set of OnFileChangeListeners listening for changes to the associated Path.

mListenerToFilePatternsMap

private final Map<OnFileChangeListener,Set<PathMatcher>> mListenerToFilePatternsMap

Mapping of OnFileChangeListeners to the Set of patterns being used to observe changes in Paths of interest.

Constructor Details

SimpleDirectoryWatchService

public SimpleDirectoryWatchService()
                            throws IOException

A simple no argument constructor for creating a SimpleDirectoryWatchService.

Throws:

IOException - If an I/O error occurs.

Method Details

cast

private static <T> WatchEvent<T> cast(WatchEvent<?> event)

Utility method used to make "valid" casts of the given event to a specific type of WatchEvent.

Type Parameters:

T - Type to which event will be casted.

Parameters:

event - Event to cast.

Returns:

event casted to WatchEvent<T>.

matcherForGlobExpression

private static PathMatcher matcherForGlobExpression(String globPattern)
                                             throws IOException

Returns a PathMatcher that performs "glob" matches with the given globPattern against the String representation of Path objects.

Parameters:

globPattern - Pattern to match against. null or empty String values will be converted to *.

Returns:

Path matching object for the given globPattern.

Throws:

IOException - if there was a problem creating the PathMatcher.

matches

public static boolean matches(Path input,
 PathMatcher pattern)

Check the given input Path against the given pattern.

Parameters:

input - Path to check.

pattern - Pattern to check against. Cannot be null.

Returns:

Whether or not input matches pattern.

matchesAny

private static boolean matchesAny(Path input,
 Set<PathMatcher> patterns)

Check the given input Path against all of the specified patterns.

Parameters:

input - Path to check.

patterns - Set of patterns to attempt to match input against. Cannot be null.

Returns:

Whether or not input matches any of the given patterns.

getDirPath

private Path getDirPath(WatchKey key)

Get the path associated with the given WatchKey.

Parameters:

key - WatchKey whose corresponding Path is being requested.

Returns:

Either the correspond Path or null.

getListeners

private Set<OnFileChangeListener> getListeners(Path path)

Get the OnFileChangeListeners associated with the given path.

Parameters:

path - Path whose listeners should be returned. Cannot be null.

Returns:

Either the Set of listeners associated with path or null.

getPatterns

private Set<PathMatcher> getPatterns(OnFileChangeListener listener)

Get the Set of patterns associated with the given OnFileChangeListener.

Parameters:

listener - Listener of interest.

Returns:

Either the Set of patterns associated with listener or null.

getDir

private Path getDir(OnFileChangeListener listener)

Get the Path associated with the given OnFileChangeListener.

Parameters:

listener - Listener whose path is requested.

Returns:

Either the Path associated with listener or null.

getWatchKey

private WatchKey getWatchKey(Path dir)

Get the monitoring "registration" key associated with the given Path.

Parameters:

dir - Path whose WatchKey is requested.

Returns:

Either the WatchKey corresponding to dir or null.

matchedListeners

private Set<OnFileChangeListener> matchedListeners(Path dir,
 Path file)

Get the Set of OnFileChangeListeners that should be notified that file has changed.

Parameters:

dir - Directory containing file.

file - File that changed.

Returns:

Set of listeners that should be notified that file has changed.

notifyListeners

private void notifyListeners(WatchKey key)

Method responsible for notifying listeners when a file matching their relevant pattern has changed. Note: "change" means one of:

• file creation
• file removal
• file contents changing

Parameters:

key - mWatchService "registration" key for one of the Paths being watched. Cannot be null.

See Also:

• run()

notifyListenersOfInvalidation

private void notifyListenersOfInvalidation(WatchKey key)

Method responsible for notifying listeners when the path they are watching has been deleted (or otherwise "invalidated" somehow).

Parameters:

key - Key that has become invalid. Cannot be null.

register

public void register(OnFileChangeListener listener,
 String dirPath,
 String... globPatterns)
              throws IOException

Notifies the implementation of this interface that dirPath should be monitored for file system events. If the changed file matches any of the globPatterns, listener should be notified.

Specified by:

register in interface DirectoryWatchService

Parameters:

listener - The listener.

dirPath - The directory path.

globPatterns - Zero or more file patterns to be matched against file names. If none provided, matches any file.

Throws:

IOException - If dirPath is not a directory.

unregister

public void unregister(OnFileChangeListener listener)

Notifies the implementation of this interface that listener should cease to be notified of file system events.

Specified by:

unregister in interface DirectoryWatchService

Parameters:

listener - Listener to unregister. Cannot be null.

unregisterAll

public void unregisterAll()

Unregisters all listeners.

Specified by:

unregisterAll in interface DirectoryWatchService

start

public void start()

Start this SimpleDirectoryWatchService instance by spawning a new thread.

Specified by:

start in interface DirectoryWatchService

Specified by:

start in interface Service

See Also:

• stop()

stop

public void stop()

Stop this SimpleDirectoryWatchService thread.

The killing happens lazily, giving the running thread an opportunity to finish the work at hand.

Specified by:

stop in interface Service

See Also:

• start()

isRunning

public boolean isRunning()

Checks to see if the service is still running.

Specified by:

isRunning in interface Service

Returns:

true if the service is running, false otherwise.

run

public void run()

Specified by:

run in interface Runnable